Now that you have it apart. You can either go a step further and remove all the internals to be able to count every gear, or just get a tooth count on the final drive gear, it's opposing gear located on the counter shaft, and the upper most gears on both the counter and main shafts to calculate the transmissions 5th and final drive gear ratios.

Once you have counted how many teeth are on each gear, you need to divide the number of teeth on the counter shaft, by the number of teeth on the main shaft to find the gear ratio. I'll give you an example using the transmission pictured. **

There are 25 teeth on the upper most counter shaft gear and 35 teeth on it's opposing gear located on the main shaft. If you divide 25 into 35, you come out with a .7142857 (.714) ratio, which is the 94+ LS transmission's 5th gear ratio.

Now using the same method, you can find the FD ratio by counting the teeth of the final drive gear, and then dividing that by the number of teeth of it's opposing gear located on the counter shaft, which would be 64 / 15 = 4.26666666 (4.266). The 94+ LS transmission's final drive ratio.

Here is a list of B series tranny gear ratios for reference purposes:
The information in this chart is for reference only, and may not be 100% accurate in all cases.

Simply an awesome write! Question. Can you use this chart to make a hybrid transmission? Say a Y21/S21 tranny with an S80 fifth gear and final drive? Logic: Short gears for acceleration with a tall 5th gear for cherry gas mileage. Oh, and any links to B20 ratios?